Carbon diffusion mechanism as an effective stability enhancement strategy: The case study of Ni-based catalyst for photothermal catalytic dry reforming of methane

Abstract

Photothermal catalytic methane dry reforming (DRM) technology can convert greenhouse gases (i.e. CH₄ and CO₂) into syngas (i.e. H₂ and CO), providing more opportunities for reducing the greenhouse effect and achieving carbon neutrality. In the DRM field, Ni-based catalysts attract wide attention due to their low cost and high activity. However, the carbon deposition over Ni-based catalysts always leads to rapid deactivation, which is still a main challenge. To improve the long-term stability of Ni-based catalysts, this work proposes a carbon-atom-diffusion strategy under photothermal conditions and investigates its effect on a Zn-doped Ni-based photothermal catalyst (Ni₃Zn@CeO₂). The photothermal catalytic behavior of Ni₃Zn@CeO₂ can maintain more than 70 h in DRM reaction. And the photocatalytic DRM activity of Ni₃Zn@CeO₂ is 1.2 times higher than thermal catalytic activity. Density functional theory (DFT) calculation and experimental characterizations indicate that Ni₃Zn promotes the diffusion of carbon atoms into the Ni₃Zn to form the Ni₃ZnC_0.7 phase with body-centered cubic (bcc) structure, thus inhibiting carbon deposition. Further, in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and DFT calculation prove Ni₃Zn@CeO₂ benefits the CH₄ activation and inhibits the carbon deposition during the DRM process. Through inducing carbon atoms diffusion within the Ni₃Zn lattice, this work provides a straightforward and feasible strategy for achieving efficient photothermal catalytic DRM and even other CH₄ conversion implementations with long-term stability.